The present invention relates to a transfer bar actuating mechanism for providing a generally cycloidal output motion of an output member in a prescribed linear path and an improved support structure for such a mechanism.
The present invention generally relates to and is an improvement upon the mechanism shown in U.S. Pat. No. 3,857,292 issued on Dec. 31, 1974 to J. H. Brems for Linear Indexing Mechanism.
The Brems mechanism provides a cycloidal action through a combination of gears including an output drive gear which is mounted on an offset crank arm of a crankshaft. The crankshaft arm is also connected to a planetary gear which is in engagement with internal teeth on a fixed ring gear. The planetary gear in turn is connected to the output drive gear. Thus, as the crankshaft is rotated about a drive axis, the planetary gear will rotate about the eccentric axis of the crank arm. At the same time the planetary gear also orbits about the drive axis of the crankshaft. The result is that the drive gear while being rotated and gear driven by the planetary gear will also be moved in a reciprocating translational motion. Thus the drive gear will rotate about an axis which moves linearly in translation from positions in line with the crankshaft drive axis to extended positions on opposite sides of that axis. An elongated drive member having a gear rack engages the drive gear in a rack and pinion type connection and is driven linearly in translation by the drive gear with the desired reciprocating cycloidal motion. The elongated drive member can be used in a manufacturing environment as a transfer bar for moving a pallet holding a workpiece into and out of different work stations.
With the Brems construction the drive gear is substantially supported only by the crank arm and the connection with the planetary gear; thus in its extended positions in translation the drive gear will encounter bearing loads which are offset from the crankshaft drive axis and from the crank arm and support connection with the planetary gear. Such bearing loads can result in wear of the engaged teeth and could also result in limitations in the load capability of the unit and/or the requirement of a larger sturdier structure for a given load requirement.
In the present invention a support structure is provided which moves in translation with the drive gear to provide additional support to the drive gear over the full range of its linear travel. This support structure also assists in maintaining good, uniform engagement between the teeth of the drive gear and the teeth of the gear rack on the drive member or transfer bar. In one form of the invention the support is provided at the axis of the drive gear such that bearing loads from the transfer bar can be resisted. In addition with the present invention the gear mechanism is located in an enclosed housing whereby a pool of lubricant can be maintained to continuously lubricate the engaged components.
It is believed that the above results in a structure which is less susceptible to wear and, because of the continuous support and uniform engagement, can be used in high load applications without the need to enlarge the load carrying members.
In addition the present invention utilizes a gear reduction assembly at the input of the mechanism configured to provide a compact structure.
Therefore it is an object of the present invention to provide an improved transfer bar actuating mechanism of the above described type in which a support structure is provided for linear translational movement with the drive gear to provide support to the drive gear throughout its range of linear travel in translation.
It is another object of the present invention to provide an improved transfer bar actuating mechanism of the above described type in which the support structure provides support to the drive gear at its axis whereby bearing loads from the transfer bar can be resisted.
It is still another object of the present invention to provide a transfer bar actuating mechanism of the above described type in which the gear mechanism is located in an enclosed housing with constant lubrication being applied.
It is another object of the present invention to provide a transfer bar actuating mechanism of the above described type utilizing a gear reduction assembly at the input while providing an overall compact structure.
It is a general object of the present invention to provide a compact drive mechanism for a transfer bar with a simple constant velocity input to provide the transfer bar with a cycloidal linear output with a desirable acceleration and deceleration and a desirable increase in velocity to a rapid intermediate movement and a final decrease to zero velocity and a unique support for the drive mechanism.
Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.